1. Field of the Invention
The present invention relates to a display device and a method of making the display device.
2. Description of the Related Art
OLED (organic light emitting diode) is a type of flat panel display that has recently become popular. Some reasons for the increase in its popularity include advantages such as low-voltage driving, light weight, slim shape, wide angular field and quick response. OLED is classified into passive matrix and active matrix types depending on the driving method that is used. The passive matrix OLED is simple to manufacture but its power consumption rapidly increases with the display size and resolution. Therefore, the passive matrix OLED is mainly employed in small-display applications.
Unlike the passive matrix OLED, the active matrix OLED is complicated to manufacture. However, it is useful in big screen and high resolution applications.
In the active matrix OLED, a TFT is connected to each of a plurality of pixel areas. Each pixel area separately controls an organic light emitting layer that emits light. A pixel electrode is disposed in each pixel area and each pixel electrode is electrically separated from the adjacent pixel electrode so that each pixel electrode is driven separately. Further, a nonconductive wall is formed between adjacent pixel areas to prevent the pixel electrodes from short-circuiting and to separate the pixel areas. Between the walls, a hole injecting layer and the organic light emitting layer are sequentially formed on the pixel electrode.
The hole injecting layer, which is usually in an aqueous suspension state, is formed by ink-jetting on the pixel area and subjected to a drying process. However, since the wall is usually made of a polymer such as polyamide, which is hydrophobic, a de-wetting phenomenon occurs around the wall causing the hole injecting layer around the wall becomes thin. Accordingly, hole injecting efficiency decreases in the region around the wall, decreasing the brightness of the OLED device.